Cyclic O,O,S-triesters of phosphorodithioic acid and process for making

ABSTRACT

Certain O,O,S - triesters of phosphorodithioic acid are excellent co-accelerators in the sulfur vulcanization of rubbers, especially EPDM rubbers, thereby making possible a considerable reduction in the cure time. Additionally, certain novel compounds of the above class and their preparation are disclosed.

United States Patent [1 1 Nudenberg et al.

[4 1 Apr. 22, 1975 l CYCLlC 0,0,S-TRIESTERS OF PHOSPHORODITHIOIC ACID AND PROCESS FOR MAKING [75] Inventors: Walter Nudenberg, West Caldwell;

Merlin P. Harvey, Passaic: James Urquhart Mann, Wayne, all of NJ.

[52] US. Cl. 260/923; 260/795 B; 260/927 R; 260/934; 260/937; 260/978 [51] Int. Cl. C07d 105/04; C08f 27/06 [58] FieldofSearch 260/923,927 R. 934. 937. 260/978 [56] References Cited UNITED STATES PATENTS 3.098.470 7/l963 Kawahara 260/937 X Primary E.\'aminerAnton H. Sutto Atlurney, Agent, or FirmRobert J. Patterson, Esq.

[ ABSTRACT Certain 0,0,S triesters 0f phosphorodithioic acid are excellent co-accelerators in the sulfur vulcanization of rubbers, especially EPDM rubbers, thereby making possible a considerable reduction in the cure time.

Additionally, certain novel compounds of the above class and their preparation are disclosed.

4 Claims, No Drawings CYCLIC 0,0,S-TRIESTERS OF PHOSPHORODITHIOIC ACID AND PROCESS FOR MAKING This is a division of application Ser. No. 66,870, filed Aug. 25, 1970 now US. Pat. No. 3,712,878 dated Jan. 23, 1973.

This invention relates to (l) the use of certain esters of 0,0-alkylene-phosphorodithioic acid to accelerate the sulfur vulcanization of rubbery elastomers at elevated temperatures (i.e., at approximately 400F and higher), (2) vulcanizable compositions containing such triesters, (3) improved cured vulcanizates produced in accordance with the foregoing use and (4) many of the triesters themselves as novel compounds.

The esters of 2,2 alkylene-phosphorodithioic acid that are within the invention are the adducts, resulting from the addition of 0,0-(2,2-dimethyltrimethylene)- phosphorodithioic acid (hereinafter referred to as DTP for convenience) or homologues across an unsaturated bond, such as, for example,

, as in styrene or alkene;

H as in benzalazine; and

, as in acetonitrile.

GEN

The compound to which DTP or its homologues add can have more than one unsaturated bond, and the additive reaction may occur at one or more of such bonds.

The structural formula of DTP is:

Accordingly, the generalized structure of the adduct can be represented as follows:

R cH -o %s c 12 CH2 s wherein R and R are alkyl groups which can be the same or different and each group can have from 1 to 5 carbon atoms, and wherein x is 1 or 2, If) portion represents the optional presence of an oxygen atom, and R is the after-addition moiety of the reactant to which DTP has been added. The R moiety can be alkyl except methyl, alkenyl, alkynyl, aralkyl except benzyl and alkyl-substituted aralkyl except alkyl substituted benzyl, an alicyclic radical (including polycyclic radicals) and the alkyl substituted derivatives thereof, and'a heterocyclic radical containing one or more heteroatoms selected from sulfur, oxygen and nitrogen. Additionally, the R moiety can contain any of the following functional substituent groups:

When R is an aliphatic compound or contains an alipreferably from 1 to 5. Examples of R radicals containphatic moiety (for instance, when R is an alkyl or an ing both non-functional and functional moieties follow.

alkyl substituted alicyclic radical), such aliphatic compound or moiety can have from 1 to 10 carbon atoms, are:

Examples of R as a monovalent radical (i.e., x=l) Mail-12?,

OK hydroxy okphenethyl 1-(dodec-y1oxyc;arbony1)ethyl 2 dode :yloxycarbonyl )e thyl A (benzylidenehydrazino )benzyl .1 2, 3a l, 7 7a-hexahydro-'-4, 7-methanoinden- -l-yl l 2 3a l 7 7a-hexahydro 4 7-me thanoinden- 3 yl 1 me thylhepsyl Qiw thylbenzyl phenethyl Examples of R as a divalent radical (i.e., x =2) are:

2,5-norbornylene &3,

m-phenylenediisopropylene -CH -CH (2methylefihylene )carboxyt rimethylene l,2-phenylenebis(carboxytrimethylene) CH CH CH SCH CH thiobisfimimethylene -=-CH CH COOCH CH OCOCH CH ethylenebis(oxycarbonylethylene) 3-methyl-l-butenylene ethylenecarboxyethjlene -CH CH CH CH p-phenylenediethylene -CH -CH -CH CH tetramebhylene -g u H 1 CH CH Z-methyltetramethylene -'3H -CH. CH ---CH 2 3-d1me thyl tetrame thylene 14 -C H -CH H tJ-I CONHC 2 2 CH ethylenecar'bonyliminotrimechylene (15 CH -CIl -CH OCH -CH -CH oxybis (trims thylene 16 '"H CH 3 3 Additional representative examples of R are ethyl, propyl, butyl, pentyl, vinyl, allyl, isopropenyl, butenyl, pentenyl, butynyl, pentynyl, phenethyl, phenylpropyl, phenylbutyl, phenylpentyl, naphthylmethyl, naphthylethyl, naphthylpropyl, naphthylbutyl, naphthylpentyl, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, decahydronaphthyl.

Representative examples of heterocyclic radicals containing one or more heteroatoms selected from sulfur, oxygen and nitrogen are dihydrothienyl, tetrahydrothienyl, 2,3-dihydrobenzothienyl, dihydrofuryl, dihydropyranyl, chromanyl, pyrrolinyl, piperidyl, indolinyl, indolidinyl, 1,3-dithiolanyl, 1,4-dioxanyl, imidazolinyl, imidazolidinyl, pyrazolidinyl, pyrazolinyl, dihydropyrazinyl, piperazinyl, dihydropyrimidinyl, dihydropyridazinyl, benzimidazolinyl, 1,2-dihydrobenzotriazolyl, dihydroquinolyl, 1,2-dihydroquinoxalinyl, dihydrooxathiinyl, thiazolinyl, isothiazolidinyl, dihydrobenzothiazolyl, oxazolidinyl, isoxazolidinyl, oxazolinyl, isoxazolinyl, dihydrooxazinyl, Z-benzoxazolinyl, oxadiazolidinyl, oxathiazolinyl.

Representative examples of alkyl substituted homologues of the aforementioned radicals are methylpropyl, methylbutyl, methylpentyl, ethylpropyl, ethylbutyl, ethylpentyl, l ,1,3 ,3-tetramethylbutyl, 4,4- dimethylhexyl, methylbutenyl, methylpentenyl, methylbutynyl, methylpentynyl, a-methylbenzyl, a-ethylbenzyl, a-propylbenzyl, a-butylbenzyl, methylphenethyl, ethylphenethyl, propylphenethyl, butylphenethyl, a-methylnaphthylmethyl, ethylnaphthylpropyl propylnaphthylbutyl, methylcyclohexyl, ethylcyclopropyl, propylcyclobutyl, methylphenycyclohexyl, ethyltetrahydronaphthyl, butyltetrahydronaphthyl.

Representative examples of alkyl substituted heterocyclic radicals are phenethyldihydrothienyl, methylbenzodihydrothienyl, propyldihydrofuryl, butyldihydropyranyl, isopropylchromanyl, butylpyrrolinyl, ethylpiperidyl, ethylindolinyl, isopropylindolinyl, methyl-1,3-dithiolanyl, ethyltetrahydrothienyl, propyl- 1,4-dithianyl, butyll ,3-dioxolanyl, methyl-1,4- dioxanyl, ethylimidazolinyl, propylimidazolidinyl, butylpyrazolidinyl, pentylpyrazolinyl, methylpiperazinyl, ethyldihydropyrimidinyl, propyldihydropyridazinyl, methyl-2,3-dihydrobenzimidazolyl, ethyltetrahydroquinolyl, propyltetrahydroquinolyl, propyldihydroquinoxalinyl, methyldihydrooxathiinyl, ethylthiazolinyl, propylisothiazolinyl, methyldihydrobenzothiazolyl, butyloxazolidinyl, pentylisoxazolidinyl, methyloxazolinyl, ethylisoxazolinyl, propyldihydrooxazinyl, methyldihydrobenzoxazolyl, propyloxadiazolinyl, butyloxathiazolinyl.

Of the 0,0,S-triesters of phosphorodithioic acid which fall within the above general formula, many have been previously reported in the literature. J. H. Bartlett (U.S. Pat. No. 3,159,664) discloses, for instance, 0,0- (2,2-dimethyltrimethylene)S-a-methylbenzyl phosphorodithioate and its method of preparation. It should be understood, however, that the latter compound has not been previously described as an accelerating agent within or without the temperature limits of the invention. Althoughsynergistic combinations of thiazole accelerators and zinc phosphorodithioate 0,0-diesters are known (see US. Pat. No. 3,308,103 to Coran), it will be hereinafter shown that such compounds are inferior accelerating agents compared with the compounds of the invention.

A new type of adduct disclosed herein is the result of the addition of DTP and its homologues to a grouping. This is a new reaction previously unreported. This type of adduct is exemplified by 0,0-(2,2- dimethyltrimethylene )S-[ a-(benzylidenehydrazino) benzyl] phosphorodithioate whose preparation is described in Example 7 below.

PREPARATION The following examples illustrate the preparation of various adducts that are within the invention.

EXAMPLE 1 This example illustrates the preparation of 0,0-(2,2- dimethyltrimethylene)S-a-methylbenzyl phosphorodithioate which is the Markovnikoff 1:1 mole addition product of 0,0-(2,2-dimethyltrimethylene) phosphorodithioic acid and styrene.

10.4 g. (0.1 mole) of peroxide-free styrene was added dropwise during five minutes to a continuously stirred solution of 19.8 g. (0.1 mole) of 0,0-(2,2- dimethyltrimethylene) phosphorodithioic acid in 200 ml. of reagent benzene at room temperature. The mixture was then stirred and refluxed for 9 hours. Evaporation of the solvent gave a liquid which crystallized very slowly. Recrystallization from cyclohexane gave a solid having a melting point of 8485.5C. The yield of recrystallized product was 9.5 g. (31.5 percent of theory).

Analysis for C l-l O PS Cald. C, 51.64; H, 6.33; P, 10.24; S, 21.21. Found. C, 51.45; H, 6.28; P, 10.01; S, 20.34.

The preparation of this particular adduct has been reported in the literature (U.S. Pat. No. 3,159,664 to J. H. Bartlett).

EXAMPLE 2 This example illustrates the preparation of the anti- Markovnikoff 1:1 mole addition product of 0,0-(2,2- dimethyltrimethylene) phosphorodithioic acid and styrene.

A mixture of 20.8 g. (0.2 mole) of commercial grade styrene, 39.6 g. (0.2 mole) of 0,0-(2,2- dimethyltrimethylene)phosphorodithioic acid in 100 ml. of reagent benzene and 0.697 g. (0.004 mole) of tert-butyl peroxypivalate (a 75 percent solution in mineral spirits) was stirred and heated at 45C for 20 minutes and then was heated to reflux. Refluxing and stirring were continued for 7 hours. A 2 m1. portion of the reaction solution was evaporated to dryness and the residue after recrystallization from Skellysolve melted at 67-71C. A second recrystallization from Skellysolve raised the melting point to 72-75C. A third recrystallization from Skellysolve raised the melting point to 75.5-77C. A fourth recrystallization from Skellysolve raised the melting point to 76-77.5C. A mixed melting point with 0,0-(2,2- dimethyltrimethylene)phosphorodithioic acid was 52-59.5C. The mixed melting point with a purified sample (melting point 84-85.5C) of the product of Example 1 (the Markovnikoff 1:1 adduct) was 5762C.

Analysis for C H O PS I Cald. C, 51.64; H, 6.33; P, 10.24; M01. wt 302.4. Found. C, 51.63; H, 6.37; P, 10.36; M01. wt 303.0.

These mixed melting points and the analyses indicate that the product was neither the recovered dithioic acid nor the product from Example 1, but was the anti- Markovnikoff 1:1 mole addition product, viz., 0,0-.

(2,2-dimethyltrimethylene)S-phenethyl phosphorodithioate.

EXAMPLE 3 This example illustrates the preparation of 0,0-(2,2- dimethyltrimethylene)S-[ 1 ,2,3a,4,7,7a-hexahydro-4,7- methanoinden-2-yl] phosphorodithioate, which is the 1:1 mole adduct of dicyclopentadiene (3a,4,7,7a-

tetrahydro-4,7-methanoindene) and 0,0-(2,2- dimethyltrimethylene) phosphorodithioic acid (DTP).

39.6 g. (0.2 mole) of 0,0-(2,2- dimethyltrimethylene)phosphorodithioic acid was dissolved at room temperature in 200 ml. of dry toluene contained in a 500 ml., three-neck, round bottom flask equipped with a stirrer, thermometer, reflux condenser and dropping funnel. To the resultant solution, while stirring continuously, was added 25.4 g. (0.2 mole) of dicyclopentadiene through the dropping funnel during a period of 10 minutes. The ensuing exothermic reaction raised the temperature of the reaction mixture to about 52C. in 10 minutes, the solution remaining colorless. After 24 hours at room temperature, the solution was placed in a beaker on a warm steam bath. As the solvent (toluene) evaporated, a white solid crystallized from solution. After 24 hours, the mixture was filtered to remove the white, solid product which weighed 54.6 g. After recrystallization from Skellysolve and airdrying, the melting point of the product was 1 l3l 16C. A second recrystallization from Skellysolve gave a product with a melting point of ll3.5-l15.5C.

Analysis for C H O PS (1:1 mole adduct): Cald. C, 54.52; H, 7.02; P, 9.37; %,S, 19.41. Found. C, 53.83; H, 6.82; P, 8.89; S, 18.08.

An infrared spectrum of the above 1:1 mole adduct showed the complete absence of absorption at 1610 cm, which is characteristic of the double bond between carbon atoms 2 and 3 in the following formula:

An absorption maximum was present, however, at

1575 cm, which is characteristic of the double bond between carbon atoms 5 and 6, indicating that the DTP had added across the double bond between carbon atoms 2 and 3.

EXAMPLE 4,

This example illustrates the preparation of 0,0-(2,2- dimathyltrimethylene)S,S bicyclo [2.2.1]heptane- 2,5-diyl)] phosphorodithioate, which is the 1:2 mole adduct of norbornadiene (bicyclo[2.2. l ]2,5- heptadiene) and 0,0-(2,2-dimethyltrimethylene) phosphorodithioic acid.

9.2 g. (0.1 mole) norbornadiene was added dropwise during 6-7 minutes to a continuously stirred solution of 39.6 g. (0.2 mole) 0,0-(2,2-dimethyltrimethylene) phosphorodithioic acid in ml. of reagent benzene at room temperature. An exothermic reaction caused the temperature of the mixture to rise to 585C. When the temperature had dropped to 40C., product began to crystallize from the reaction mixture. Filtration of the mixture gave 39.0 g. of product (79.9 percent of theory). The melting point (l84l94C.) of the crude product was raised to l94-l95C. by recrystallization from hot cyclohexane.

Analysis for C H O P S (1:2 mole adduct):

Cald. C, 41.79; H, 6.19; P, 12.68; mol. wt., 488.6.

Found. C, 41.28; H, 5.89; P, 12.74; mol. wt.,

EXAMPLE 5 This example illustrates the preparation of 0,0-(2,2- dimethyltrimethylene )S-( l-methylheptyl) phosphorodithioate, which is the adduct of 1-octene and O,- O-(2,2-dimethyltrimethylene)phosphorodithioic acid. 5

11.2 g. (0.1 mole) of l-octene was added to 19.8 g. (0.1 mole) of 0,0-(2,2-dimethyltrimethylene)phosphorodithioic acid at room temperature. An exothermic reaction did not occur. After heating the reaction mixture at 100C. for 8 hours, it was placed under reduced pressure (35 mm.) at a temperature of 75-85C. on a rotary evaporator for 2 hours. The residual, viscous liquid weighed 30.3 g. (98 percent of theory).

Analysis for C H O PS Cald. C, 50.29; H, 8.76; P, 9.97; S, 20.66. Found. C, 49.92; H, 8.64; P, 9.84; S, 20.0.

EXAMPLE 6 This example illustrates the preparation of 0,0-(2,2- dimethyltrimethylene)S,S'-[2,2'-(1,3-phenylene)diispropylene] phosphorodithioate, which is the adduct of 2 moles of 0,0-(2,2-dimethyltrimethylene) phosphorodithioic acid and 1 mole of m-diisopropenylbenzene.

15.8 g. (0.1 mole) of m-diisopropenylbenzene, which had been purified by passage through chromatographic alumina, was added dropwise while stirring for six minutes to a solution of 39.6 g. (0.2 mole) of 0,0-(2,2- 30 dimethyltrimethylene) phosphorodithioic acid in 150 ml. of reagent benzene at room temperature. A slightly exothermic reaction caused an elevation of 5C. in the temperature of the reaction mixture. After stirring for 1 hour, the mixture was heated to, and maintained at, 60-65C., with continuous stirring, for 5 hours. Evaporation of the solvent left a crystalline product, covered with a thin layer of clear viscous syrup. The melting point of the crude solid, after washing with Skellysolve, was 1 1 1.5-l 15C. Recrystallization from a 4:1 mixture of cyclohexane and benzene gave 24.3 g. of product (43.8 percent of theory for a 2:1 adduct). Another recrystallization from a 5:1 mixture of Skellysolve and chloroform gave a product melting at 109.5l16C.

Analysis for C l-1 O P S (2:1 mole adduct): Ca1d.% C, 47.62; 1-1, 6.54; P, 11.17; S, 23.12; mol. wt., 554.7.

Found. C, 47.32; H, 6.32; P, 11.18; S, 25.60; mol. wt., 582.0.

EXAMPLE 7 This example illustrates the novel preparation of O,- O-(2,2-dimethyltrimethylene)S-[a-(benzylidenehydrazino)benzyl] phosphorodithioate, which is the adduct of 1 mole of 0,0-(2,2-dimethyltrimethylene) phosphorodithioic acid to 1 mole of 1,2-di(benzylidene)-hydrazine (the latter being the condensation product of 2 moles of benzaldehyde and 1 mole of hydrazine).

To a solution of 39.6 g. (0.2 mole) of 0,0-(2,2- dimethyltrimethylene) phosphorodithioic acid in 150 ml. of reagent benzene was added, dropwise, with continuous stirring over a period of 5 minutes as 25C., a solution of 20.8 g. (0.1 mole) of l,2-di-(benzylidene)- hydrazine. The resultant mild exothermic reaction caused the temperature of the mixture to rise 5C. and within 15 minutes a yellow precipitate began to form.

Stirring was discontinued after a total of 2 /2 hours, after which the mixture was filtered to isolate the yellow product which had a melting point of l31.5-135.5C. Recrystallization of the yellow product from a mixture of 1 liter of cyclohexane and 0.5 liter of benzene gave 28.3 g. of product melting at l32135C. A second recrystallization raised the melting point to l35l36C.

Analysis for C H N O PS (1:1 mole adduct): Cald. C, 56.14; H, 5.70; P, 7.62; S, 15.78. Found. C, 54.81; H, 5.78; P, 7.77; S, 15.33.

The elemental analysis indicated that the product obtained was a 1:1 molar addition product of the phosphorodithioic acid and the azine. The yield of product before recrystallization was 37.3 g. or 91.9 percent of theory.

EXAMPLE 8 This example illustrates the preparation of 0,0-(2,2- dimethyltrimethylene)S-(oxo)-a-hydroxyphenethyl phosphorodithioate. This is the 1:1:1 mole adduct of 0,0-(2,2-dimethyltrimethylene) phosphorodithioic acid, styrene and oxygen.

To a solution of 39.6 g. (0.2 mole) of 0,0-(2,2- dimethyltrimethylene)phosphorodithioic acid in ml. of reagent benzene in a Parr oxygenator bottle was added 20.8 g. (0.2 mole) of styrene. The bottle was placed quickly into the oxygenator and 40 pounds of oxygen pressure from an oxygen cylinder was applied while shaking the reactants. Within 2 hours, a mild exothermic reaction occurred during the uptake of 0.129 moles of oxygen. The reaction mixture was cooled to room temperature. The solid product, weighing only 2.5 grams after drying, was filtered off. The reaction mixture filtrate was diluted with ml. of toluene, washed with 2 100 ml. portions of 8 percent aqueous sodium bicarbonate solution, one (1) 100 ml. portion of water, then freed of solvent and dried under reduced pressure (2 mm. at 70C. for 2 hours). The weight of the very viscous, amber-colored, taffy-like residue was 37 g. (55.3 percent of theory).

Analysis for C l-1, O PS Cald. C, 46.69; H, 5.73; P, 9.26. Found. C, 48.41; H, 5.62; P, 9.02.

An infrared spectrum of the chemical, (C H, O.,PS showed absorption maxima at: (1) 3450 cm (presence of OH group); (2) 685 cm" (presence of P=S grouping); (3) 1050 cm" and 990 cm' (presence of P-O-C grouping).

The reaction of the previous example is not unique. Thus the addition of DTP according to the disclosure in the presence of oxygen under pressure results in the S-'(oxo)-a-hydroxyform of the resultant compound. For example, in the case of Example 5, 0,0-(2,2- dimethyltrimethylene)S-( 0x0 )-2-hydroxy-n-octyl phosphorodithioate; and in the case of Example 10, lauryl 3-[0,0-(2,2-dimethyltrimethylene)S-oxo phosphorodithioyl]-2-hydroxypropionate.

EXAMPLE 9 This example illustrates the preparation of lauryl 2- [0,0-(2,Z-dimethyltrimethylene)phosphorodithioyl] propionate, which is the 1:1 mole adduct of 0,0-(2,2- dimethyltrimethylene) phosphorodithioic acid to lauryl acrylate.

To a solution of 19.9 g. (0.1 mole) of 0,0-(2,2- -Continued dimethyltrimethylene) phosphorodithioic acid in 70 ml. of methylene chloride was added 24 g. (0.1 mole) Chemlcamame of lauryl acrylate in small P01110115 over a period of D 04Hzldimmhyltrimethylene)S [L2, about one-half hour. The reacnon m1xture was then re- 3a,4,7,7a-hexahyd ro-4,7-methanoindene-2' fluxed for 2%. hours and then washed successively with E llZQ PJEfSSPEgfiZ lane) S S, 50 ml. of saturated, aqueous sodium bicarbonate solu- 1,ic i 2 .2.1pi e tane-z js-di n @11 tion and 100 ml. of distilled water. The washed solution F g fzg It th I S l was then treated with Darco (activated charcoal), filfi i ;ggf g ggg g gggl tered and evaporated. The resldual l1qu1d was placed G 0,0-(2,2-dimethyltrimethylene)S,S'- under reduced pressure (3 mm.) for 5 hours at 90C. i g gg giggt e y fl prOpylene] blsphos- The weight of the clear viscous liquid was 36.2 g. (yield H 0,0-(2,a-dimeth ltri ieth lene)S-[a- 82.4 percent of theory, calculated as the 1:1 mole adfi g f y razmo)benz l1 phosphoroduct). An infrared spectrum showed the absence of the 1 0,042,2 dim&thy1trimethy|ene)$ (QXO)- the r lacr l to ahydroxyphenethylphosphorodithioate VH2] i i g g g fg f of lau y y a K Lauryl 2-[0,0(2,2-dimcthyltrimethylene-) na ySlS O1 39 4 2- phosphorod1th1oyl]propionate Cald. C, 54.77; H, 8.96; P, 7.06. Found. C, 55.70; H, 8.85; P, 7.07.

The elemental analyses showed that the chemical was The compound formula (Base Formulation) used in the 1:1 mole adduct as indicated above. 20 this evaluation was:

Use of the Phosphorodithioic Esters as Accelerators p b1: weight In the process of vulcanizing rubbers, it is desirable ggg g ig 9 to accelerate the vulcanization rate so that the produc- Circosol 2XH** 25.0 tion efficiency of a given size vulcanization unit can be g gg fz g 5.8 increased. One approach to this result has been to raise S lf 5 the vulcanization temperature, but the resulting vul- Z-MeYCQPIObBHZOIhIQZOIB 183.0 caqlzates have Shown themselves to be of Inferior qual An ethylene-propylcne-dicyclopentadicne tcrpolymer (EPDM) having an iodine 1ty 1n several respects. The present compounds, on the nurznlbzcrr: 10,9231 ethylene-propylene ratio Oreo-4o andaMooney visc0sity(ML-4 at .)o other hand are y good co'accelerators of the sulfur A naphthenic-type oil; specific gravity 0.9279. Saybolt viscosity at 210F. vulcanization process at elevated temperatures (1.e., at 61 Rwnds Color ASTMY Aniline P least about 350 to 400F) when used in combination with such primary accelerators as the thiuram sulfides Two known P l accelerators pp and disulfides, the dithiocarbamates and the thiazoles. Pounds A and R (tetramethyllhlul'alfl It thus becomes possible to shorten the cure time very monosulfide) f B 15 a 21116 dlester of phosphorodlthlsubstantially. For example a 30 minute cure at 320F. l [Zmc l l y 'l y P 9 can be Shortened to just 5 minutes at phorodithioate]. The part1cular Z11'1C phosphorodithio- The following demonstrates the use of the chemicals companon purposesfs'lmfi2 whlch m of the invention. Normally they function as accelerabmanon wlth MBT gwes a synefgltlqeffecl when used tors and generally can be used with any conventional to accelerate the sulfur vulcan1 zat1on of ethyleneaccelerator, e.g., a thiazole, a dithiocarbamate, a thiupropylene terpolyn'lers thlazole-type F e ram monosulfide, a thiuram disulfide or a sulfenamide tor 333081103 Comm- Chemlcal? C type accelerator to l and K are the eight chemicals whose preparauon is given in the above examples 1, and 3-9, inclusive. Two different cures, viz., (1) a 30 minute cure at Code Name 320F., and (2) a 5 minute cure at 400F., were used. A Tetmmethylthiumm monosumde Stress-strain data, including Shore A hardness results, B j q y -P y p p were obtained on test pieces which had been vulca- C 181 5; nized in a press at the two different temperatures indimethylbenzyl phosphorodithioate cated.

Table I Stock l 2 3 4 5 6 7 8 9 10 ll 12 Base Formulation 183 183 183 183 183 183 183 183 183 183 183 182.5 (MBT 0.5) Chemical A 1.5 B 3.0 C 3.0 D 3.0 E 3.0 F 3.0 G 3.0 H 3.0 1 3.0 J 3.0 K Property For 30 Minute Cure at 320F. Shore A 59 47 52 52 47 57 56 52 34 47 46 (I)Tensile,psi 3210 3350 840 1730 820 940 2800 3230 1170 245 1040 500 (2)El0ng.,7c 510 570 1070 900 1000 980 640 640 1000 1140 950 1000 (3)S-300,psi 1170 915 210 325 210 215 700 710 245 225 I30 Bloom* 2 l l l l l 1 Table I Continued Stock 1 2 3 4 5 6 7 8 9 l 1 l 12** Property For Minute Cure at 400F. Shore A 56 49 52 53 55 51 55 57 55 42 Tensile. psi 3220 1870 2760 2660 2620 2560 2850 2820 3190 1750 Elongation, '70 620 790 780 720 750 790 610 750 590 810 S-300, psi 820 405 525 525 455 465 735 805 525 260 Bloom 3 4 l l 1 l 2 2 2 1 After one l week at room temperature: I none; 2 very slight; 3 moderate; 4 heavy (I) Tensile strength at break (2) Ultimate elongation (3) Modulus of elasticity at 30071. elongation Base formulation without 0.5 pt of MBT The results given in Table 1 show that the chemicals 5 flexure as in the case of a pneumatic tire or a belt. Ap-

of the invention acting as co-accelerators give good high temperature (e.g. 400F.) sulfur cures; substantially equivalent to the cures obtainable with prior art accelerators such as the thiuram sulfides and the zinc diesters of phosphorodithioic acid. The comparison of the high temperature (400F.) curewith the standard temperature (320F.) cure shows incipient reversion in the Monex stock (A) and appreciable reversion of the zinc diester stock B). Stocks C to I show that adequate physical properties were developed after only 5 minutes at 400F. with no evidence of reversion. It is obvious that satisfactory cures can be obtained at temperatures between 320 and 400F. and above by proper adjustment of the cure time. An outstanding characteristic of the chemicals of this invention is that, unlike the prior art accelerators, they produce vulcanizates with very little or no bloom, thereby making them especially useful in injection molding formulations.

The accelerators of the invention can be used to accelerate the sulfur vulcanization of both low and high unsaturation rubbers.

The EPDM rubbers are prepared by interpolymerizing a monomeric mixture containing ethylene, a higher alpha monoolefin containing 3-16 carbon atoms and a polyene having two or more carbon-to-carbon double bonds. The preferred polyenes include dicyelopentadiene, 1,4-hexadiene, 1,3-pentadiene, cyclooctadiene, cyclooctatetraene, tridecadiene, S-methylene-Z- norbornene, 5-ethyIidene-2-norbornene 5-a-propylidene-2-norbornene, 5-isopropylidene-2- norbornene, 5-n-butylidene-2-norbornene,

5 -isobutylidene-2-norbornene 5 2-methyl-2- butenyl )-2-norbornene, 5 3 -methyl-2- butenyl )norbornene and 5 3 ,5-dimethyl-4-hexenyl 2-norbornene.

The inventive accelerators are particularly useful in the production of vulcanized rubber articles reinforced with polyester (linear terephthalate polyester) fibers such as those. described by Daniels in US. Pat. No. 3,051,212 and Chantry in US. Pat. No. 3,216,187. These rubber articles include pneumatic tires, V-belts, flat belts, Timing belts (toothed power or synchronizing belts), footwear, coated fabrics, rubberizedfabric containers, etc. When these articles are made using a rubber vulcanizing system with the so-called delayed action accelerators such as the thiurams or the sulfenamides, it has been found that these accelerators exert a deleterious effect on the polyester fiber reinforcement. This deleterious effect is accentuated when the article is subjected to elevated temperatures in service, such elevated temperatures arising from environmental heat and/or internal heat generated by repeated parently these accelerators during the cure and/or in service form a basic environment which accelerates hydrolytic and/or chain scission of the polyester molecules which in turn causes degradation in the physical properties of the composite article.

The inventive accelerators are uniquely suited as co- 7 Vulcanizing Agent parts/ parts rubber Sulfur 1.0 2.5

Tuex (tetramethylthiurarn 2.0 4.0 disulfide) Ethyl Tuex (tetraethylthiuram 2.5 4.5 disulfide) Vultac (alkyl phenol disulfides) 5.0 12.0 Sulfasan R (4,4-dithiodimor- 4.0 6.0 pholine It should be understood that the particular sulfurcontaining vulcanizing agent selected and the amount thereof used for vulcanization are not critical to the practice of the inventive technique; the type and quantity of vulcanizing agent used need only be that as would effect vulcanization under ordinary prior art conditions.

Typical prior art accelerators with which the inventive accelerators can be used are, in addition to MBT and MBTS:

Sodium Z-mercaptobenzothiazole Zinc Z-mercaptobenzothiazole 2 ,2 '-dithiobisbenzothiazole 2-(morpholinothio)-benzothiazole 2-benzothiazolyl l-hexamethyleniminecarbodithioate 2benzothiazolyl thiolbenzoate 1 ,3-bis( 2-benzothiazolylmercaptomethyl)urea 2-( 2 ,4-dinitrophenylthio )benzothiazole S-( 2-benzothiazolyl)N-diethyl dithiocarbamate N-cyclohexylbenzothiazole-2-sulfenamide N-tert-butylbenzothiazole-2-sulfenamide In general, the weight ratio of the inventive accelerator to the prior art accelerator is from 1:1 to 5:1, with about 2:1 preferred. The rubber compositions which can be cured with the inventive accelerators can contain the usual added additional ingredients, such as sulfur, pigments, antioxidants and/or antiozonants, fillers, extenders, etc. Curing temperatures can range up to about 400F. and higher depending upon such wellunderstood factors as the time of cure, and the type of rubber, prior an accelerator, activator, etc., used.

Of course, it is readily apparent to those skilled in the art, that there are variations of the invention which can be made without departing from its scope and spirit, and all such variations which basically rely on the teachings disclosed herein are considered to be within the scope of the foregoing description and appended claims.

Having thus described our invention, what we clairri and desire to protect by Letters Patent is:

l. A compound having the following formula:

wherein R, and R are C to C alkyl groups which can be the same or different, the portion represents the optional presence of an oxygen atom; and R is a-( benzylidenehydrazino)benzyl.

2. A compound having the following formula:

reaction mixture.

UNITED STATES PATENT AND TRADEMARK OFFICE CERTIFICATE OF CORRECTION PATENT NO. 3,879J 97 DATED April 22, 1975 |NVENTOR(5) 3 Walter Nudenberg; Merlin P. Harvey; James U. Mann it is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 17, lines 17-25, the formula should appear as follows:

Column 18, lines 4-10, the formula should appear as follows:

R CH O S R2 CHE-""0 S Signed and Scaled this fourth Day of November 1975 [SEAL] A ttes t:

C. MARSHALL DANN Commissioner of Parents and Trademarks RUTH C. MASON Arresting Officer 

1. A COMPOUND HAVING THE FOLLOWING FORMULA:
 1. A compound having the following formula:
 2. A compound having the following formula:
 3. The compound cyclic O,O-2,2-dimethyltrimethylene S( Alpha -(benzylidenehydrazino)benzyl) phosphorodithioate. 